1. Field of the Invention
The present invention relates to a liquid ejection apparatus configured to eject liquid onto a recording medium to form an image thereon.
2. Description of the Related Art
There is conventionally known an ink jet recording apparatus including a liquid ejection head configured to eject ink onto a recording medium to record an image thereon. As an internal structure of the liquid ejection head, ink chambers each for storing ink are superposed on each other in an up and down direction, and upper portions of the ink chambers respectively have air-discharge openings for discharging air bubbles from the inside of the ink. Provided in each of the air-discharge opening is a seal member. Each of the air-discharge openings is connected to a pump for placing the corresponding ink chamber under negative pressure. The seal member allows gas to be discharged and inhibits liquid from being discharged.
When air bubbles are discharged from the inside of the ink, the pump is operated to suck air bubbles accumulated in an upper portion of the ink chamber. A liquid level of the ink stored in each ink chamber rises, and accordingly the ink is brought into contact with the seal member. This contact is performed before the liquid level of the ink becomes higher than the air-discharge openings, preventing the ink from moving to a position higher than the air-discharge openings. This construction prevents the ink from being discharged from the air-discharge openings and allows only the air bubbles from being discharged.
In general, the liquid ejection head has an ejection surface which is to face a recording medium and formed with a multiplicity of ejection openings for ejecting ink. Such a liquid ejection head typically carries out a purging operation for maintaining and recovering ink ejection characteristics. This purging operation is an operation for discharging the ink from the ejection openings by applying a pressure to the ink in the ink chambers or by applying a suction pressure to the ink in the ejection openings.